Three free programs available. Post or Email if interested casagiannoni@optonline.net :

I have always been fascinated by the phenomenon of depth perception or
stereo vision. It would seem that this is a combination of two
mechanisms.

First there is the focus position of the eye. This doesn't depend on 2
eyes and will work well with one eye. It also is independent of image distances, though great distances will all be nearly the same.

Then, there is the slight though very significant difference between
the perceived images in the left and right eyes, owing to the
difference in horizontal positions of the eyes. This is much greater
at closer image distances and dependant on both eyes. It is my
perception, that at all close or reasonably limited distances, that
this is a greater part of depth perception.

Programs Stereo 1, -2 and -3 generate special images to test this
second mechanism. These depend on deliberately misaligning eyes in
such a way that the two orange dots at the top of the image are spilt
and resolved into three images. This is achieved by staring as to more
distance objects, which will shift the left image to the right and the
right image to the left. When the images resolve to three, with the
overlapped images in the center, the eyes are set to perceive depth in
the image.

The image consists of a narrow random display of dots extending top to
bottom, where this displayed area is repeated horizontally across the
image width, with the same spacing as between the three orange dots.
The eyes will lock on the display where each eye is actually locked on subsequent repeats of the display. Now, the display has deliberately
been altered in the horizontal direction at various areas of the whole
image, such that the eyes will perceive an apparent shift in angular
position of these areas, which will be perceived as a different depth
via the second mechanism. A very neat trick that works surprisingly
well !

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